In accordance with global warming and the development of economics and industries advancing on a worldwide scale, efforts to reduce energy consumption is becoming important. Based on such a background, distributed-type power supply systems represented by a solar power generation system are becoming popular (see, for example, Patent Literatures 1 and 2). In addition, as an emergency power supply at the time of disaster, interests in such distributed-type power supply systems are nowadays increasing.
As to a distributed-type power supply system installed in a standard home, it is prohibited to provide generated and stored power to a commercial power system except from solar power generation systems. Hence, in order to make a distributed-type power supply available at the time of, for example, blackout, it is desirable to separate a power system at home (home power system) from a commercial power system.
According to distributed-type power supply systems, however, it is difficult to keep supplying power to all electric apparatuses installed at home. Therefore, when a commercial power system is recovered, it is necessary to quickly interconnect the home power system with the commercial power system.